Genuine Toro OEM (Fits Exmark) 139-2399 Cog Belt for Toro Timecutter and Exmark Quest Riding Mowers, Black

What It Is

This is a genuine OEM cog belt (part #139-2399) that drives the mower deck blades on select Toro TimeCutter and Exmark Quest zero-turn riding mowers. It’s designed as a direct replacement for the original belt to restore cutting performance.

Fitment & Compatibility

Before buying, confirm your machine’s model and deck size. This belt fits:

• Toro TimeCutter models with 42-inch, 46-inch, and 50-inch fabricated decks (e.g., SS4225, SS4625, SS5000, and similar).
• Exmark Quest models with 42-inch, 48-inch, and 52-inch fabricated decks (e.g., QST225, QZT225, QST235, QZT235).
• Also compatible with some Toro Z-Master and Exmark Lazer Z models with the same deck sizes—check your owner’s manual or existing belt part number.

Measure your old belt: this is a 1/2-inch wide, cogged belt with a 96.5-inch effective length. Ensure your deck pulley configuration matches—this belt uses a serpentine routing (usually around three pulleys and two idlers). OEM fit is guaranteed; aftermarket belts may vary in tension or durability.

Key Things to Know

• Quality: Genuine Toro OEM belt—reinforced rubber with Kevlar-like tensile cords for longer life under heavy use. Holds up better than cheap aftermarket belts.
• Installation: Moderate difficulty—requires removing the deck and using a wrench to release tension on the idler pulley. A belt routing diagram is often printed on the deck or in the manual; take a photo before removing the old belt.
• Common gotcha: This belt is directional—the cog side rides against smooth pulleys, the flat side on the engine pulley. Installing it backward can cause slippage and premature wear.
• Expect life: 1–2 seasons of regular mowing (50–100 hours) depending on debris and tension. Replace immediately if you see cracks, fraying, or glazing.

Should You Buy It

Buy this if you own a Toro TimeCutter or Exmark Quest with a 42–52 inch fabricated deck and want a drop-in, reliable OEM replacement. It’s the right choice for restoring blade speed and avoiding downtime—skip cheap knockoffs if you mow more than once a week.